Maxillofacial growth after neck burn injury at a young age : an experimental study in the rabbit

An experimental model was designed to define alterations in the normal mandibular growth process under the influence of postburn neck contractures. Additionally, this craniofacial growth model was used to compare two early treatment modalities of neck burns in their capability to minimize contracture and hence allow for normal mandibular growth and development. Growth implies increase in size as well as change in shape and position. These three aspects of growth were defined accordingly to Björk as rotations. The intramatrix rotation expresses the change in mandibular shape, and the matrix rotation expresses the change in mandibular position relative to surrounding structures. The total rotation expresses both, and together with the measurement of the mandibular length, they represent the increase in mandibular size. Thirty-two 7-week-old rabbits were divided at random in four groups of eight rabbits each and randomized for selection for the 14 operation days defined as t = 0: Group A: controls to define normal mandibular growth Group B: untreated third-degree neck burns Group C: third-degree neck burns treated by a full-thickness skin graft Group D: third-degree neck burns treated by a myocutaneous flap All animals underwent placement of two bone markers in the maxilla. With biweekly intervals, standardized lateral skull roentgenographs were taken until the rabbits reached the age of 21 weeks. In this time period, major growth accelerations including the pubertal growth spurt took place. By the use of 13 reference points and 7 reference lines, rotations and distances were calculated. Statistical analysis of the data was performed. The results show that the normal mandibular length was unaffected in all groups. There were no statistically significant changes in matrix, intramatrix, and total rotations of the mandible and the maxilla. There was a statistically significant difference in the displacement of the mandibular reference point between all groups, suggesting a variable degree of normal backward skull rotation, namely, due to group B. Explanations to be considered concerning the fact that the only minor differences were found in group B: 1. Drawbacks of the animal model: differences in skin texture, postnatal mandibular growth, and head position compared with those of humans. 2. Other functional adaptation mechanisms such as changes in head position, which are recruited at first in adapting to disturbances of homeostasis, were not measured. Soft-tiss